The present invention relates to an arrangement for welding bags. More particularly, it relates to an arrangement of welding staggered bags with inner plies coated by a synthetic plastic material. The staggered bags with inner layers coated by a weldable synthetic plastic material are much easier to manufacture than the staggered bags with inserted bottom-closed sacks of polyethylene. However, such bags could not be produced in a simple way with completely moisture-impermeable bottoms. Complete moisture tightness in these staggered bags can be attained only in the case when the coated inner layers are completely welded over the entire width of the staggered bag. Special problems which took place here is that hot air supplied from a heating apparatus for welding must be supplied between opposite parts of the inner layer in the region of the end portion of a staggered tube to be welded. However, this is absolutely necessary to provide reliable welding of the entire bag width of the inner layer of the tube.